Sainsbury City Diesel MPG

[DogVanMan]

Has anyone experienced poor MPG with Sainsbury City Diesel..?

I run a Td5 110 with Porny's stage 2 mods (top bloke) and I'd swear I've been down on power and getting worse MPG over the last (full) tank of Sainsbury City Diesel. This is first time I've tried the stuff.

Over 275 miles of mainly motorway I've been down to 23.3mpg. I'd have expected at least 25mpg, probably better. (Porny's mods have actually made it slightly more economical at small and steady throttle openings, and although I've seen better than 30mpg on a steady run, this tankful wasn't an economy run!). After filling up at Sainsbury's, I noticed that it felt a little flat too. I Googled it and there are comments on other car forums to similar effect. Needless to say I've gone back to my usual stuff now.

Anyone noticed anything about Sains City Diesel in a Land Rover..?

G

[andycallaghan]

Sainsbury's is the same as BP fuel, so what do you normally fill up with?

[adafish]

I'VE TRIED THE bp ultimate today in the 300tdi...put £30 in at 101.8p a ltr, see how i do on that

[DogVanMan]

I'm normally on Total or Shell standard diesel.

I think there are different additives in Sains City Diesel to reduce smoke, so it may well be different to standard BP diesel?

Another one to throw in.. Do I have it right that for petrol there are standards concerning RON valies (95, for example) but for diesel fuel there is no standard as to the minimum level of calorific value (If that's the right term to use here)?

G

[andycallaghan]

I'm normally on Total or Shell standard diesel.

I think there are different additives in Sains City Diesel to reduce smoke, so it may well be different to standard BP diesel?

Another one to throw in.. Do I have it right that for petrol there are standards concerning RON valies (95, for example) but for diesel fuel there is no standard as to the minimum level of calorific value (If that's the right term to use here)?

G

The more RON, the better the performance.
However, I think the "Ultimate" in diesel relates to the emissions, not the performance.

[DogVanMan]

Agreed, higher RON value for petrols = Higher performance,  all other things being equal (and if the engine can use the higher octane)

Higher cetane rating for diesels has a similar effect, I think.. Question is, can pump diesel be any cetane rating by law?

G

[Range Rover Blues]

The RON number is the octane, measured as the resistance to self-ignition so a waste of time putting higher RON in if you don't increase C:R or timing.

[DogVanMan]

Yep, I understand that for petrol engines. For diesels, the cetane rating is similar to octane for petrol?

And specifically is it possible/likely that Sains City Diesel is lower cetane rating that other pump diesels? I'm sure it hasn't performed as well in MPG terms but I wonder if anyone else has had similar experience or can shed any light..?

G

[Ridgeback]

Don't know about Sainsburys Diesel but I was getting very poor MPG from Tesco Diesel.
In my 200tdi you can only notice a small difference but in my BMW 530D it makes a huge difference. Load of flat spots and the MPG is way down.
530 miles to a tank with Tesco 600+ with Shell.

[Range Rover Blues]

Yep, I understand that for petrol engines. For diesels, the cetane rating is similar to octane for petrol?

And specifically is it possible/likely that Sains City Diesel is lower cetane rating that other pump diesels? I'm sure it hasn't performed as well in MPG terms but I wonder if anyone else has had similar experience or can shed any light..?

G

Cetane rating works the other way, but as few people have heard of it I didn't mention it.  Now, somewhere at the back of my brain I think that a "reference" fuel is made up of Octane and Cetane :-k, 95 RON being equivelent to 95% ovtane, 5% cetane.  Anyhoo, a high octane is obvioulsy a poor cetane and vice-versa.  With Derv fuel we want them to self-ignite at combustion temperatures.

As for whether there is a standard for Cetane number I don't know.

[DogVanMan]

Ridge, RRB thanks..

Ridge, interesting that, because in my old 300tdi I could throw Millers Power Plus in and it made little difference, on the Td5 with additive and before the mods it certainly felt a little better and MPG figures were improved. I alternated between tankfuls with and without additive for over 2000 miles and it was consistently worse without additive. I used to keep an eye on the mileage with the 300 tdi and I never noticed a measurable difference. Not very scientific but a good indication, I think. Perhaps the electronic management of the more modern engines can make better use of better fuel??? Dunno.

RRB. That makes perfect sense.. I hadn't thought of it like that, yes we do want diesel fuel to self ignite quicker! Also explains why additive manufacturers refer to 'improved' cetane figure, not 'higher'.

I'd love to see a list of cetane ratings for different pump diesel fuels (and especially Sains City Diesel), but I guess it doesn't exist. Unless anyone knows different..?

G

[Range Rover Blues]

I can tell you the cetane ratiing of bio is worse.

As for additive, I guess it was down tot he relative effeciencies of both engines, the TD5 would be "programmed" to self tune with the changes in fuel hence the improvement in performance or economy.  The 300 bless it will just plod along with whatever c**p you put in there.  You could in theory tune a 300 to make the best of the best fuel, but heaven help you if you fill up with tat.

[ChrisV8]

Over the years and with a number of vehicles I have found that I get much poorer MPG and performance from supermarket diesel, my Jeep is very poor getting about 40mpg on Supermarket but up to 50 using Shell, yesterday on a trip to Brum and back 48mpg and I got there in under 2.1/2 hrs from here 150 miles !!

I worked in Aberdeen with a TD5 90 and only once put supermaket diesel in it and it was awful, no go and very thirsty. The tanker may go to the same place for a fill, but they don't put all the additives in supermarket stuff I am told, me I stick to Shell for all our vehicles cos it works best and generally is no more than the supermarket as they tend to compete on price as well.

[Range Rover Blues]

Our local branded stuff doesn't price match the supermarket, so I have to think about whether the extra MPG pays me to use it :-k